I. Field of the Invention
The present invention relates generally to shock absorbers and, more particularly, to shock absorbers having an adjustable dampening force and of the type used on automotive vehicles.
II. Description of Related Art
Modern day shock absorbers of the type used on automotive vehicles typically include an elongated pressure tube having a piston slidably disposed within the pressure tube. The piston divides the pressure tube into a first and second working chamber on opposite sides of the piston.
An elongated piston rod is attached to the piston so that the rod moves in unison with the piston. The rod and piston are movable both in an extension direction and a compression direction. In the extension direction, the piston rod extends outwardly from the pressure tube. Conversely, in the compression direction, the piston rod is retracted into the pressure tube.
A cylinder is disposed around and spaced outwardly from the pressure tube thus forming a reservoir in the shock absorber. A control orifice and adaptive valve are then fluidly connected in series between one of the working chambers and the reservoir. Restriction of a flow between the first working chamber and the reservoir thus dampens the force applied to the shock absorber in the extension direction. In addition, one-way valves formed between the reservoir and the second working chamber, as well as check valves and restricted orifices formed in the piston, allow flow between the first and second working chambers in a controlled and dampened fashion. The working chambers as well as the reservoir are filled with hydraulic oil.
One disadvantage of these previously known shock absorbers occurs during severe events, such as when the vehicle tire encounters a pothole. In this event, the extreme and rapid movement of the shock absorber in the extension direction can result not only in damage to the tire, but even structural damage to the wheel.
Ideally, movement of the shock absorber in the extension direction should be limited during severe events, such as when the vehicle tire encounters a pothole, while still permitting rapid movement of the vehicle tire and shock absorber in the compression direction. Although there have been attempts to control the operation of the software to meet these design criteria, such intelligent software have not proven wholly successful and are also expensive to implement.